I don't have any old golf balls. I usually hit enough into the water and woods to need a new box next time I play.
It looks like a great handle though. Maybe someday when I finish a round and still have a few balls left I will give it a try.
I liked these handles and ordered dozens of each size so I had them on hand at reasonable prices. For needle files I used a pin vise or a collet type handle I had.
The golf ball would be safe and effective but would just not work for me. I like a better index of position and orientation for control. Just a matter of individual preference. I also took some common sized files and ground off the tangs. I rounded and smoother the butt end for comfort in the hand. I was big on not using files with bare tangs. I saw too many driven through palms when used on lathes. I warned one guy and offered him a handle as I always had spares in my box. He said he didn't have timne to waste on such things. A short time later he drove a tang through his hand and decided he had a few days to spare while it healed. He was the foreman's brother so he got away with such things. He liked to call toolmakers "slow machinists" but when he could not manage a job you would hear lots of cussing from his machine and he would call in sick the next day. I usually got stuck with the job and knew I would find all the extra parts scraped and the tools broken, with no extra time to replace them. He was predictable enough I called it ahead several times. I liked the hard jobs but hated going into the job short of time and already short parts.
When I worked as an aircraft mechanic, I had some wood handled file handles that tightened onto the tang by a bolt in the end. That closed steel jaws in the top. I don't think a ball shape handle would help me stay parallel with the work.
I also used the smaller file handles to make deburring tools. I would take dull or broken taps, screw them tightly into the handle, then grind the shank of the tool to the shape I wanted. These worked very well. I also used 1/8" pin vices to hold used center drills or the round shanks of carbide circuit board drills. I made a fixture for accurate triangular grinding of these and kept a supply of sharpened bits in my box. I had a source for used circuit board drills for $.15 each by the hundred. I would just break off the drill and the shank was a 1/8" blank of high grade fine grain carbide. I also made holder to use these in the lathe and the mill. They could be ground into excellent small fly cutters and boring tools.
I worked at one screw machine shop that did large batches of incredibly fine parts. We had graduated microscopes used to grind the tools used to precision lengths and angles. They had a spec. deburring room with a staff of ladies who often worked in tiny parts under magnifying lamps. Some work was so critical that companies required anyone deburring their parts to take classes and be certified at their facilities. I had done a lot of this kind of work for Sandisk when I had my first shop so I knew the type of tools needed. The ladies in there always had a hard time getting their tools sharpened as everyone was busy. When they found out I kept a stash of excellent and very sharp bits in my box I became real popular. They would bring out 4 or five and ask me to sharpen them and I would just exchange them and sharpen them after hours. I was the only manual machinist in this CNC shop and often worked on contract so I had a lot of flexibility in my hours.I did end up getting cookies and cake brought to me on a number of occasions. I was well looked after.
A very versatile tool I used a lot was a triangular file, 1/4" or so, with the tang ground off and the end smoothed and polished, and the tip ground into a triangular scraper. This was very handy as the file could beburr outer edges and the tip could do holes and inside corners or curves, Very handy around the mill or lathe, I always have a couple set up this way..